There are various types of radiation imaging cameras available including gamma ray cameras and neutron cameras. Two types of imaging gamma detectors are in wide use. Gamma cameras used for nuclear medicine are descendants of the Anger camera and consist of a scintillating crystal viewed by an array of photo multipliers (PMTs). See Anger H O. "Scintillation Camera," Rev Sci. Instr. 1958; 29: 27, which is hereby incorporated by reference herein. When an incident energetic penetrating particle is absorbed by a crystal, it produces a scintillation event. The total measured scintillation is used to determine the radiation energy. Its position is determined by centroiding the location on the array of PMTs. The intrinsic spatial resolution is limited by the size of the PMTs and the Poisson statistics of the scintillation. These detectors typically have intrinsic resolution of several mm with arrays of 50-100 PMTs.
A second type of gamma detector consists of an array of photosensitive crystals such as ZnCdTe. These detectors have better energy resolution than the Anger camera since their photo detection efficiency is much greater than the product of the scintillation efficiency and the subsequent PMT quantum efficiency. However, it is currently very expensive to fabricate an array with many pixels. These detectors have found application in coded aperture gamma-ray astronomy detectors with up to thousands of discrete pixels.
Another type of ionizing radiation camera is designed to locate neutrons. Two-dimensional position sensitive neutron detectors are currently limited in either their spatial or temporal resolution. Scintillator-based detectors similar to the Anger camera have only modest spatial resolution as do He.sup.3 thermal neutron detectors. As compared to the scintillator and He.sup.3 detectors, CCD-based detectors have good spatial resolution, however they are not counting detectors and therefore have poor temporal resolution. Additionally, CCD-based detectors lack the ability to discriminate gamma rays from neutrons. This limits neutron imaging of special nuclear material and use of neutron scattering for diagnostic purposes and nondestructive testing.